Understanding E Liquid: The Technology Behind Vaping It's NOT just water vapor. Vaping exposes your lungs to harmful chemicals and can affect your overall health. This Vaping Awareness Month, get the facts and free support to quit. Text READY Electronic cigarette Simple English Wikipedia, the free encyclopedia What's in an e liquid or vape juice? The main ingredients are propylene glycol (PG) and vegetable glycerine (VG). These are solvents that are basically used to dissolve and carry the other ingredients.